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   Re: [xml-dev] ANN: xpath1() scheme for XPointer

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> At 02:33 PM 10/26/2002 -0400, Elliotte Rusty Harold wrote:
> >Another tricky bit about using XPaths on post-included documents is that 
> >you can get very different documents depending not only on whether the 
> >XIncludes are resolved but how the different fallbacks play out. The most 
> >obvious case is something like //chapter[1] which could select different 
> >chapters depending on which includes got resolved or not. Furthermore, 
> >they're a lot of XPath functions like string() or number() that take a 
> >node-set as an argument, but really only operate on the first node in that 
> >set, so which node is first can be very important, even if you don't see 
> >an explicit positional dependence.
> >
> >I also suspect the following, sibling, following-sibling, and 
> >preceding-sibling axes could well give significantly different results 
> >depending on which includes got resolved and which didn't. I don't think 
> >the ancestor, child, descendant, self, attribute, namespace etc. axes 
> >would be affected.
> I think I'm just going to have to note that these are possibilities in the 
> I-D, and let people sort them out in their own processing systems.

This is best.  After all, you needn't introduce XInclude to see the issues 
Elliotte mentions.  XML's optional entity and DTD processing puts paid to 
that.  The return value of count(@*) will never be an invariant across all 
XPath processors for a large class of docuemnts.  This fact has not, as far as 
I know, put anyone's eye out.

Uche Ogbuji                                    Fourthought, Inc.
http://uche.ogbuji.net    http://4Suite.org    http://fourthought.com
Python&XML column: 2. Introducing PyXML - http://www.xml.com/pub/a/2002/09/25/p
The Past, Present and Future of Web Services 1 - http://www.webservices.org/ind
The Past, Present and Future of Web Services 2 - 'http://www.webservices.org/in
Serenity through markup - http://adtmag.com/article.asp?id=6807
Tip: Using generators for XML processing - http://www-106.ibm.com/developerwork


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